Hayward 4-wire Remote Interface

Hi, new to this forum and I have a rather off-the-wall question. So, please forgive me if this isn’t an appropriate place to ask it.

I have a Hayward Aqua Plus (model PL-PLUS) controller for my saltwater pool. This unit has a 4-wire connection for a wired remote control. I’d like to instead connect a homebrew Arduino project. It’s partly for remote functionality, partly because it’s a hobby of mine.

Anybody have information on the electrical spec for this interface or the communication protocol used? Could be as simple as power, ground and RS232 TX / RX? Or, maybe half-duplex RS485?